The long-term goal of this project is to form a description of the development of object perception early in life. Current developmental research into object perception has failed to take advantage of the plethora of theoretical and empirical work present on this topic in the adult literature, and thus a complete and comprehensive description of the development of object perception is not yet available. The proposed research will use adult theories of object perception to guide the construction of a description and analysis of object perception during early development. This description will expand our understanding of young infants' ability to represent the visual world to levels beyond the simple ability to distinguish between sensory primitives, such as brightness and contrast. Three major points are addressed: (1) Is the visual system capable of forming a perceptual representation of shape at 3 months? This question will be tested using precise stimulus controls that have never before been applied to the study of infant visual perception. This test will establish a new benchmark for the ontogenetic beginning of shape representation. (2) Do young infants possess the ability to perceive the same real world entity from different views of a single volume (a cone, brick, cylinder, etc.), and if not, does this ability develop? This ability is called viewpoint invariant perception. Several adult theorists argue that viewpoint invariant perception of single volumes, or volumetric primitives, is critical to object perception, because these volumes may be the primitives, or building blocks used to represent objects. Whether these primitives actually exist in infant vision, and whether they function early in development, has never been explored. (3) When does the ability to perceive two different views of a complex object as the same real-world entity (viewpoint invariant object perception) emerge, and how do infants accomplish this task? These questions will be addressed using multiple measures of infant visual perception. Addressing these questions will narrow the gap between what is known about object perception in infants and the information available regarding adult perception. A basic understanding of how this process functions will aid in developing theories and guiding research into the development of categorization as well as object perception because the invariant perception of single objects may serve as the basis for the development of perceptual similarity- based categorization. The description constructed from the proposed research will assist in understanding the deviations from normal development in object perception and object categorization present in various types of developmental disorders, including autism.